The present invention relates to catheter balloons for medical devices. In particular, the present invention relates to biaxially oriented semi-compliant catheter balloons comprising acrylonitrile polymers, acrylonitrile copolymers, and acrylonitrile blends. The present invention further comprises methods of making such catheter balloons.
Catheter balloons are extensively used in medical applications such as angioplasty, valvuloplasty, urological procedures, and tracheal or gastric intubation. Catheter balloons are generally made using non-compliant materials (e.g., polyethylene terephthalates, polyacrylenesulfide, and copolyesters), compliant materials (e.g., polyvinyl chloride [PVC], polyurethanes, crosslinked low density polyethylenes [PETs], and highly irradiated linear low density polyethylene [LDPE]), or semi-compliant materials (e.g., nylon, and polyamines). Some of the desirable attributes for catheter balloons include high tensile strength (to avoid bursting under pressure and to dilate tough lesions), controlled compliance (to avoid overinflation and subsequent vessel damage), flexibility (to facilitate retraction through vessels), moisture resistance (to avoid loss of mechanical strength), ease of coating with drugs or lubricants, and ease of bonding to a catheter material.
However, no single prior art catheter balloon material offers all of the above-discussed desirable characteristics. For example, while non-compliant balloon materials have the advantage of high tensile strength, this same property makes them resistant to folding and reshapability with the result that they are difficult to retract through vessels. Although decreased wall thickness may overcome folding resistance, it nevertheless results in xe2x80x9cpinholing,xe2x80x9d which is associated with a fragility during insertion and the need for extreme care in handling, as well as possible damage to surrounding tissue caused by high pressure fluid leakage. Additionally, because catheter balloons of non-compliant materials do not inflate beyond a particular distended profile, they cannot be tailored to fit the changing diameter of physiological vessels. Non-compliant materials suffer from the added drawback that they do not readily accept coatings and are difficult to bond to other materials (e.g., catheter materials) due to their higher melt temperatures which resist melting adhesion, and polymer polarity which resists biocompatible adhesives.
Similarly, catheter balloons made of compliant materials exhibit some undesirable characteristics. Compliant balloons are characterized by the ability to continually distend with increasing pressure, thus causing additional distention of the treated vessel. However, this property also risks overinflation of the catheter balloon and subsequent vessel damage. The risk of overinflation is exacerbated by the low tensile strength of compliant materials, which results in balloon burst failure and vessel injury. Though this risk may be reduced by increasing the balloon""s wall thickness, the resulting balloons resist folding (i.e., winging) and are more cumbersome to use because of their rigidity.
Catheter balloons which are constructed of art-known semi-compliant materials also possess undesirable properties. For example, while known semi-compliant balloon materials combine the advantages of relatively high tensile strength and controlled compliance, they nevertheless continue to exhibit pinholing, difficulty in coating and bonding with other materials, and excessive material shrinkage. Semi-compliant nylon materials suffer from the additional disadvantage of being hygroscopic, thus suffering from accelerated loss of mechanical strength.
Thus, what is needed is a catheter balloon having relatively high tensile strength, controlled compliance, reduced tendency for pinholing, ease of coating with and of bonding to other compounds, as well as resistance to moisture.
The invention provides a catheter balloon comprising biaxially oriented acrylonitrile polymer. In one preferred embodiment, the balloon is within its glass transition state at approximately human body temperature. Without intending to limit the invention to a particular wall thickness and tensile strength, in an alternative preferred embodiment, the acrylonitrile polymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. While not intending to limit the invention to a particular tailored compliance, in a more preferred embodiment, the tailored compliance of said acrylonitrile polymer catheter balloon is from approximately 5% to approximately 15%. In an alternative embodiment, the acrylonitrile polymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0015 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
The invention further provides a catheter balloon comprising biaxially oriented acrylonitrile copolymer. Without limiting the invention to any particular components, in one embodiment, the acrylonitrile copolymer comprises acrylonitrile and methyl acrylate. Without limiting the invention to any particular components and/or proportions of components, in a preferred embodiment, the acrylonitrile copolymer comprises from approximately 73 to approximately 77 parts by weight of acrylonitrile and from approximately 23 to approximately 27 parts by weight of methyl acrylate, said acrylonitrile copolymer being sold under the trademark xe2x80x9cBAREX 210(trademark).xe2x80x9d In a more preferred embodiment, the BAREX 210(trademark) balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0012 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile copolymer catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile copolymer catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the acrylonitrile and methyl acrylate copolymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0012 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
Also without limiting the invention to particular components and/or proportions of components, in an alternative preferred embodiment, the acrylonitrile copolymer comprises from approximately 73 to approximately 77 parts by weight of acrylonitrile and from approximately 23 to approximately 27 parts by weight of methyl acrylate, said acrylonitrile copolymer being sold under the trademark xe2x80x9cBAREX 218(trademark).xe2x80x9d In a more preferred embodiment, the BAREX 218 (trademark) catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile copolymer catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile copolymer catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the BAREX 218(trademark) catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
Also provided by the invention is a catheter balloon comprising biaxially oriented acrylonitrile blend. Without limiting the invention to any particular components, in one embodiment, the acrylonitrile blend comprises acrylonitrile and polyethylene elastomer. Without intending to limit the invention to any particular proportion of components, in a preferred embodiment, the acrylonitrile blend comprises approximately 70 parts by weight of acrylonitrile and approximately 30 parts by weight of polyethylene elastomer. In a more preferred embodiment, the polyethylene elastomer catheter balloon has a mean wall thickness of from approximately 0.00065 inches to approximately 0.0015 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile blend catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile blend catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the acrylonitrile and polyethylene elastomer blend catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0012 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
Also without limiting the invention to any particular components, in an alternative embodiment, the acrylonitrile blend comprises acrylonitrile and a block copolymer comprising crystalline polybutylene terephthalate and amorphous long chain glycols, said block copolymer being sold under the trademark xe2x80x9cHYTREL(trademark).xe2x80x9d While not intending to limit the invention to any particular proportion of components, in a preferred embodiment, the acrylonitrile blend comprises approximately 70 parts by weight of acrylonitrile and approximately 30 parts by weight of HYTREL(trademark). In a more preferred embodiment, the acrylonitrile and HYTREL(trademark) blend catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile blend catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile blend catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the acrylonitrile and HYTREL(trademark) blend catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
Without limiting the invention to any components, in another alternative embodiment, the acrylonitrile blend comprises acrylonitrile and polyether block amide. In a preferred embodiment, the acrylonitrile blend comprises approximately 60 parts by weight of acrylonitrile and approximately 40 parts by weight of polyether block amide. In a more preferred embodiment, the acrylonitrile and polyether block amide blend catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile blend catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile blend catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the acrylonitrile and polyether block amide blend catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres,. reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated. burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
The invention additionally provides methods for making biaxially oriented catheter balloons, comprising: a) providing a material selected from the group consisting of acrylonitrile, acrylonitrile copolymer, and acrylonitrile blend; b) extruding said material to form an extruded tube; c) heat setting said extruded tube to form a heat set tube; d) longitudinally drawing said heat set tube to form a drawn tube; e) radially expanding said drawn tube to form a balloon member; and f) heat setting said balloon member to form a heat set balloon member. Without limiting the means and/or temperature of extrusion, in one embodiment, extruding is performed in a die comprising a barrel zone, and wherein said die is at a temperature of from approximately 500xc2x0 F. to approximately 560xc2x0 F. and said barrel zone is at a temperature of from approximately 400xc2x0 F. to approximately 470xc2x0 F. In a preferred embodiment, the method further comprises after step b), quenching said extruded tube in a water bath at approximately 22xc2x0 C. In a more preferred embodiment, the distance between said water bath and said die is from approximately 0.2 inches to approximately 1.0 inches.
In an alternative embodiment, the tube is extruded at a drawdown ratio of less than 3:1. In a preferred embodiment, the drawdown ratio is approximately 2:1.
In another alternative embodiment, the heat setting is at a temperature of from approximately 60xc2x0 C. to approximately 80xc2x0 C. 
In yet another alternative embodiment, the heat setting is for a period of at least approximately two hours.
In a further alternative embodiment, the time between said heat setting and said extruding is less than approximately eight hours.
In another alternative embodiment, the drawing is at a tube draw temperature between the first order glass transition temperature and the second order glass transition temperature of said material. In a preferred embodiment, the tube draw temperature is from approximately 300xc2x0 C. to approximately 450xc2x0 C. In an alternative preferred embodiment, the length of said drawn tube is from approximately 2 times to approximately 5 times the length of said extruded tube.
In a further alterative embodiment, the radially expanding is at a blow up ratio of from approximately 5.25:1 to approximately 7.25:1.
In yet another alternative embodiment, the ratio of mean wall thickness of said heat set tube to said heat set balloon is from approximately 15:1 to approximately 20:1.
In another alternative embodiment, the heat setting of said balloon member comprises raising the temperature of said balloon member to a heat setting temperature greater than the glass transition temperature of said material to form a heated balloon member, followed by cooling said heated balloon member to a temperature below the glass transition temperature of said material. In one preferred embodiment, the heat setting temperature is from approximately 90xc2x0 C. to approximately 180xc2x0 C. In another preferred embodiment, the glass transition temperature is from approximately 180xc2x0 C. to approximately 240xc2x0 C. In yet another preferred embodiment, the temperature below the glass transition temperature is from approximately 20xc2x0 C. to approximately 25xc2x0 C.